Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$52.52	11.874%	$58.7562	$58.76	$58.75	$58.80
Purchase #2	$88.83	13.333%	$100.6737	$100.67	$100.65	$100.70
Purchase #3	$91.41	4.142%	$95.1962	$95.20	$95.20	$95.20
Purchase #4	$135.69	8.587%	$147.3417	$147.34	$147.35	$147.30
Purchase #5	$188.40	10.691%	$208.5418	$208.54	$208.55	$208.50
Purchase #6	$106.46	4.332%	$111.0718	$111.07	$111.05	$111.10
Purchase #7	$193.35	13.402%	$219.2628	$219.26	$219.25	$219.30
7 purchase totals =	$856.66		$940.8442	$940.84	$940.80	$940.90